The present invention relates to the field of communications, and, more particularly, to phased array antennas.
Antenna systems are widely used in both ground based applications (e.g., cellular antennas) and airborne applications (e.g., airplane or satellite antennas). For example, so-called xe2x80x9csmartxe2x80x9d antenna systems, such as adaptive or phased array antennas, combine the outputs of multiple antenna elements with signal processing capabilities to transmit and/or receive communications signals (e.g., microwave signals, RF signals, etc.). As a result, such antenna systems can vary the transmission or reception pattern of the communications signals in response to the signal environment to improve performance characteristics.
For example, each antenna element typically has a respective phase shifter, programmable delay element, and/or attenuator associated therewith. The phase shifters/attenuators/delay elements may be controlled by a central controller, for example, to adjust respective phases/attenuations/delays of the antenna elements across the array. Thus, it is possible to perform beam shaping or steering on the transmitted signals to target specific geographical locations, or conversely to focus the antenna such that only signals coming from a certain direction will be received.
One example of a beam steering module for a phased array antenna is disclosed in U.S. Pat. No. 5,027,126 to Basehgi et al. The module includes a plurality of registers each for storing a control word for a respective phase shifter. The control words are provided by a controller. Steering logic within the module sequentially applies each of the control words from the plurality of registers to a control input of a respective phase shifter. Furthermore, the control words are stored in a temporary register bank until all of the control words have been received. The contents of the temporary memory register bank are then transferred to the plurality of registers so that new control words can be received while the steering logic is sequentially applying each control word to its respective phase shifter.
A stated goal of the above patent is to reduce beam settling time. In typical prior art antennas, a host will issue a beam control command (e.g., a beam steering command) prior to the instant when it is to be implemented. The host will subsequently issue a synchronizing pulse that controls precisely when a previously-sent beam steering command is to be implemented. Yet, in many phased array antennas the settling time required to implement the synchronization pulse and allow the beam to settle to the new pointing angle may be in the tens or even hundreds of microseconds. Such relatively lengthy beam settling times may equate to appreciable and undesirable signal outages during this interval. Yet, prior art approaches such as that disclosed in the above patent are generally limited in their ability to precisely manage and distribute synchronization timing and distribution. This may be the result of relatively large uncertainties in the time needed for processing the host synchronization pulse and distributing synchronization control signals, for example.
In view of the foregoing background, it is therefore an object of the invention to provide a phased array antenna having reduced beam settling times and related methods.
This and other objects, features, and advantages in accordance with the present invention are provided by a phased array antenna which may include a substrate and a plurality of phased array antenna elements carried by the substrate. The phased array antenna may also include a plurality of antenna element controllers for the phased array antenna elements and a central controller for providing beam steering commands and an edge trigger synchronization signal for the antenna element controllers, for example, based upon host beam steering commands and host synchronization signals. Furthermore, each of the antenna element controllers may store a respective next beam steering command and implement the respective next beam steering command as a respective active beam steering command responsive to the edge trigger synchronization signal from the central controller.
More particularly, the phased array antenna may also include a distribution network connecting the central controller to the plurality of antenna element controllers. The central controller and the distribution network may cooperate to deliver the edge trigger synchronization signal substantially simultaneously to all of the antenna element controllers. Further, the central controller may include a multiplexer switchable between a normal state for delivering beam steering commands to the antenna element controllers and a synchronization state for delivering the edge trigger synchronization signal (e.g., from the host) to all of the antenna element controllers. Each antenna element controller may detect the edge trigger synchronization signal from the central controller only during a predetermined time window.
In addition, each antenna element controller may include at least one holding register for storing the next beam steering command. Further, each antenna element controller may include at least one active register for storing the active beam steering command. The phased array antenna may further include at least one array subgroup controller connected between the central controller and a subgroup of the antenna element controllers. Also, the beam steering commands may include at least one of a phase value, attenuation value, and delay value.
A method aspect of the invention is for operating a phased array antenna as described above. The method may include using the central controller to provide edge trigger synchronization signals (e.g., from the host) and, at each of the antenna element controllers, storing a respective next beam steering command and implementing the respective next beam steering command as a respective active beam steering command responsive to the edge trigger synchronization signal from the central controller.
More particularly, using the central controller may include using the central controller to deliver the edge trigger synchronization signal substantially simultaneously to all of the antenna element controllers. Additionally, the central controller may include a multiplexer, and the method may further include switching the multiplexer between a normal state for delivering beam steering commands to the antenna element controllers, and a synchronization state for delivering the edge trigger synchronization signal to all of the antenna element controllers.
Further, each antenna element controller may detect the edge trigger synchronization signal from the central controller only during a predetermined time window. Also, at least one array subgroup controller may be connected between the central controller and a subgroup of the antenna element controllers, and the beam steering commands may include at least one of a phase value, attenuation value, and a delay value.